This invention relates to synthetic analogues of naturally occurring antiviral 2xe2x80x2,5xe2x80x2-oligoadenylates wherein the analogues are conjugated to a carrier molecule to enhance cellular uptake.
It is well established that the natural antiviral pathways ubiquitous in mammalian cellsxe2x80x94the (2-5xe2x80x2)oligo(A) synthetase/RNase L cascade and the PKR antiviral pathwayxe2x80x94are activated on virus infections, including HIV-1 [2-5]. Both pathways require dsRNA. which on the one hand activates (2xe2x80x2-5xe2x80x2)oligo(A) synthetase converting ATP into 2xe2x80x2-5xe2x80x2-linked oligoadenylates (xe2x80x9c2-5Axe2x80x9d) with a 5xe2x80x2-terminal triphosphate function. These unusual oligonucleotides bind and activate RNase L leading to the degradation of viral RNA and subsequent inhibition of protein synthesis [3][4]. On the other hand, dsRNA-dependent PKR (p68 kinase) undergoes autophosphorylation and catalyzes phosphorylation of the xcex1-submit of eIF-2, thereby inhibiting initiation of protein synthesis [6]. Although, (2xe2x80x2-5xe2x80x2)oligoadenylates are rapidly inactivated by two different nucleases, the (2xe2x80x2-5xe2x80x2)oligo(A)system represents a chemotherapeutic possibility for the control of virus and cell growth.
Many (2xe2x80x2-5xe2x80x2)oligo(A)derivatives have been synthesized with the aim to increase biological activity and to avoid premature decomposition of the antivirally active substance. One of the modified (2xe2x80x2-5xe2x80x2)oligo(A)analogues is the cordycepin-trimer core (2xe2x80x2-5xe2x80x2)d3xe2x80x2(A-A-A) [7][8]; U.S. Pat. No. 4,464,359 which was found to be biologically active, metabolically stable, and not toxic to cells [9]. Although, the trimer-cordycepin core effects no activation of RNase L [10]; this substance inhibits HIV-1 production [11] probably by weakening the complex formation of primer tRNALys,3 to HIV-1 reverse transcriptase [5][12][13].
One of the major problems in application of oligonucleotides to cells and biological systems is their polyanionic structure which renders them difficult to penetrate cell membranes. Numerous efforts have been made to improve the cellular uptake of oligonucleotides, e.g., incorporation in liposomes [14] or syntheses of lipophilic conjugates [15-17]. The attachment of cholesterol, various vitamins, and lipids to the 2xe2x80x2-O- and 5xe2x80x2-O-position of the sugar moiety of monomeric and trimeric cordycepin has been described [18-20].
Compounds of the following formula are provided, useful in treating viral infection in plants and animals: 
wherein:
n is from 1 to 8, preferably 1, 2 or 3, most preferably 1 or 2;
R1 is selected from the group consisting of 
wherein m is zero, 1, 2, or 3; and 
wherein q is from 1 to 20, preferably from 2 to 8, most preferably from 3 to 7;
R2 is independently selected from the group consisting of oxygen and sulfur;
R3 is independently selected from the group consisting of hydrogen and hydroxyl; and
R4 is selected from the group consisting of hydrogen, hydroxyl and 
R5 is selected from the group consisting of hydroxyl and 
R6 is selected from the group consisting of 
and 
wherein x is from 1 to 20, preferably from 2 to 16, most preferably 10 to 14;
provided that one of R1, R4 and R5 is 
wherein R6 is defined as above;
or water soluble salt thereof.
Preferably, the compounds of the invention include at least one nucleotide residue which is cordycepyl, that is, either R4 is hydrogen or at least one of R3 hydrogen. Most preferably, the compounds of the present invention comprise conjugates of 2xe2x80x2,5xe2x80x2-oligocordycepin wherein the internucleotide linkages comprise phosphodiester groups, that is, all R2 are oxygen, R4 is hydrogen, and all R3 are hydrogen.
The invention also comprises a method of treating viral infection in mammals or plants by administering an antivirally effective amount of a compound according to the above formula, or a water-soluble salt thereof. The invention also comprises an antiviral composition comprising such a compound or water soluble salt in combination with an agricultural carrier or pharmaceutical carrier.
Compounds of the invention include, for example, the following compounds, the 5xe2x80x2-mono-, di-, and triphosphates thereof, and water-soluble salts of any of them:
3xe2x80x2-deoxyadenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxyadenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxy-2xe2x80x2-O-[6-(tetradecanoylamino)-hexanoyl]adenosine;
3xe2x80x2-deoxyadenylyl-(2xe2x80x2,5xe2x80x2)-3xe2x80x2-deoxyadenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxy-2xe2x80x2-O-{-[(3xcex1,7xcex1, 12xcex1-trihydroxy-5xcex2-cholan-24-oyl)-amino]hexanoyl}adenosine;
3xe2x80x2-deoxyadenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxyadenylyl-(2xe2x80x2-5xe2x80x2)-2xe2x80x2-O-{6-{{N-{4-{[(2-amino-1,4-dihydro-4-oxopteridin-6-yl)methyl]amino}benzoyl}-L-xcex3-glutanyl}amino}hexanoyl}-3xe2x80x2deoxy]adenosine;
Compounds of the invention further include, for example, the following compounds, and water-soluble salts thereof:
3xe2x80x2-deoxy-5xe2x80x2-O-[6-(tetradecanoylamino)hexanoyl]adenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxyadenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxyadenosine;
3xe2x80x2-deoxy-5xe2x80x2-O-{6-[(3xcex1, 7xcex1, 12xcex1-trihydroxy-5xcex2-cholan-24-oyl)amino]hexanoyl}adenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxyadenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxyadenosine; and
5xe2x80x2-O-{6-{{N-{4-{[(2-amino-[,4-dihydro-4-oxopteridin-6-yl)methyl]amino}benzoyl}-L-xcex3-glutanyl}amino}hexanoyl}-adenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxyadenylyl-(2xe2x80x2-5xe2x80x2)-3xe2x80x2-deoxyadenosine.